Religious films - true religious films that actually look at the question of faith in an intelligent manner - tend to be few and far between. They either tend to be tediously pious or hysterical in their condemnation. Agnes of God is that rare beast that manages to be both questioning and respectful at the same time, while telling an engrossing story.

Psychologist Dr Martha Livingston (Jane Fonda) has been given a case that no-one else particularly wants to handle - a newborn baby has been found dead in a cloistered covenant on the outskirts of Montreal. The baby belonged to a young Sister, Agnes (Meg Tilly) who is now the subject of state deliberation as to whether or not she is mentally sound and fit to stand trial for murder or manslaughter. Livingston is sent to investigate Agnes, while under the watchful and suspicious eye of Mother Miriam (Anne Bancroft), the superior of the nunnery.

Jewison's film, I think, is one that is genuinely interested in asking what place religion has in society and for people who perhaps cannot understand the complexities of its teachings - for someone who's a lapsed Catholic sliding towards Agnosticism, it's a though provoking film that brought to mind years of religious teaching at school, particularly the idea that religion can be seen as a shelter for all. Agnes is certainly someone who views religion as a shelter; simple minded and incredibly naive (she's unable to fully describe to Livingston how babies get made) she was abandoned by her parents as a young child and was taken in by the nuns and thus has complete happiness in her faith. Yet this happiness in her faith has led to someone taking advantage of her and her resolute belief in God's workings means that she's completely unable to comprehend that what has happened is wrong and there is a human to blame, not God. Add that to her extreme beliefs in the Bible's teaching - she starves herself and refuses to sleep on a comfortable bed as she believes that will please Him - and at first glance, you may think Jewison is deeply critical of the faith, but he's not, not really. For all her fundamentalist beliefs, there's every other nun concerned at what she's doing and that includes Miriam, far from the monster a more cliched film would paint her as. The fact that Jewison achieves this balancing act on a contentious subject without appearing to be sitting on the fence, whilst telling a compelling mystery is to his immense credit. Who's the father? Who really knew about her pregnancy? Why is Agnes really there? They're questions that could be tawdry or ludicrous, but they're eased into the film in a subtle manner that keeps the plight of Agnes front and centre for most of the film.

Tilly pulls off a really strong piece of acting as Agnes, all the more tricky when you consider how easily it could have gone wrong. Prone to delusions (she keeps seeing a woman, possibly her mother), fanciful dreams and wide-eyed bursts of naive foolishness, she could have been portrayed as a loon or an idiot. Tilly doesn't however, and with her remarkable features (those eyes...) she really does seem like someone who has been 'touched' in more than one way. Fonda, with a cigarette permanently jammed in her fingers, is too big for the film, however. She's a star, and knows it, but has rarely shown the capacity to downplay herself for the sake of the film. She's not actively bad, but she tends to grandstand with the material, which contrasts not at all well with Tilly's naturalism or Bancroft's grounded underplaying - she makes Miriam an elusive character, someone deeply immersed in her faith, but pragmatic; protective of Agnes, but even more protective of any secrets that her order may be hiding. It's a shame that Fonda doesn't really have the same instincts for the dialogue that Tilly and Bancroft do, it's those two thoughtful actresses that provoke the questions long after the credits roll.

As well as Fonda's performance there are other flaws that stop Agnes of God turning from a very good film into a great one - there is a potentially interesting stigmata storyline that peters out into nothing and the denouement feels a little rushed. But it asks question rarely asked in an intelligent manner and Tilly's performance in particular is something very special indeed.